The pdfs are stored in the subfolder of the project name.
So, my project location is
C:\Trimble\Projects\ACTIVE\1000-CUNFS\10-19-18 SW TOWER STAKEOUT.vce
There should be a sub folder
C:\Trimble\Projects\ACTIVE\1000-CUNFS\10-19-18 SW TOWER STAKEOUT\
If you were to look in there it should have all your imported files as well as the PDFs images
C:\Trimble\Projects\ACTIVE\1000-CUNFS\2-21-18 NORTH FORK SIPHON\SURV CONTROL_Page001_Dpi300_Layer043.png_tiles
That needs to be transferred over to your server as well. Not just the VCE.